Along with many of their arguments and what they believe is proof, my all time favorite is how they look for gaps in science and think AH SCIENCE CANT EXPLAIN X IT HAS TO BE RELIGIOUS!
Ah, the famous "God of the Gaps" argument.
It is understandable behavior, of course. We all do it, to a degree, replacing gaps in our knowledge with various personal suppositions. It's pretty typical human behavior.
Another one I like is "science can't prove there's no god" this obviously works both ways, but the big difference is that science attempts to provide solid proof whereas religion relies solely on faith and very little proof.
Ah, yes, positive belief until the negative can be demonstrated... which I'm pretty sure is fallacious, because the logical default assumption in deduction should always be negative until demonstrably positive.
Nothing wrong with personally believing something when there's no reason not to, of course. Holding a personal belief is not necessarily presenting it as an argument that others
must accept.
What's your favorite argument?
I've always chuckled at the various ways I've seen some Omnigod binary-morality monotheists (that is, monotheists who believe in an omnipotent, omnibenevolent, and omniscient God, along with a moral system of objective "good" vs "evil") try to get around the Problem of Evil. "God has a plan", "God moves in mysterious ways", "it's all Satan's fault", "humans are all sinful by nature", etc.
'Course, such a thing is actually not terribly common to religion, as most religions (being
not Omnigod binary-morality monotheistic) don't even have a problem of evil.
I honestly find anti-religious stuff to be even sillier, especially when it's not even accurate. ...then again, it's not funny when anti-religious historical revisionism actually ends up becoming the accepted common conception of history, as in the Myth of the Flat Earth.